1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing unit such as a personal computer and a method of manufacturing the suspension.
2. Description of the Related Art
A hard disk drive (HDD) used for an information processing unit has magnetic or magneto-optical disks to write and read data and a carriage. The carriage is turned around a spindle by a positioning motor.
The carriage is disclosed in, for example, U.S. Pat. No. 4,167,765. This carriage has arms, a head suspension (hereinafter referred to also as “suspension”) attached to each arm, and a head attached to the suspension. The head has a slider. When each disk of the HDD is rotated at high speed, the slider slightly floats above the disk and air bearings are formed between the disk and the slider.
The suspension consists of a load beam, a flexure, and a base plate. The load beam is made of a thin precision resilient plate. The flexure is made of a very thin plate spring fixed to a front end of the load beam by, for example, laser welding. The base plate is fixed to a base of the load beam by, for example, laser welding and is fixed to each arm of the carriage.
Disks of recent HDDs are designed to densely record data and revolve at high speed. It is required, therefore, to provide a head suspension of improved vibration characteristics to carry out precision positioning of a head on a disk surface, as well as resistance to turbulence caused by the disks revolving at high speed. In addition, the suspension must be ready for intricate processes to provide new functions.
To deal with a high-density disk, the suspension must have high rigidity and a low spring constant. FIG. 1 shows a head suspension 101 for a disk drive according to a prior art. The suspension 101 has a load beam 103 that is solidly composed of a rigid part 103a of L1 in length and a resilient part 103b of L2 in length. It is hardly possible for this suspension 101 to simultaneously realize high rigidity for the rigid part 103a and a low spring constant for the resilient part 103b because the rigid part 103a and resilient part 103b are integrated with each other.
The material and thickness of the rigid part 103a are restricted by the resilient part 103b, and therefore, the rigid part 103a must improve the rigidity thereof by bends 105 or embossed ribs 107 that need additional precision processes to increase costs.
The bends 105 and ribs 107 disturb air flows and are easily influenced by turbulence due to disks rotating at high speed, to flutter the load beam 103.
The load beam 103 is fixed to a base plate 109, which is attached to a carriage arm of an HDD. To stably support the load beam 103 with the base plate 109, the base of the load beam 103 must not be thinner than a specified thickness. This restriction prevents the lowering of the spring constant of the resilient part 103b. 
A flexure 111 is fixed to the load beam 103. The flexure 111 has a head 113 including a slider 115.
A technique of lowering the spring constant of a load beam is disclosed in Japanese Unexamined Patent Publication No. 9-191004. This technique partly thins a resilient part of a load beam by partial etching. The partial etching, however, has a limit in precisely controlling the thickness of the resilient part, and therefore, causes variations in the thickness and spring constant of the resilient part.
Japanese Unexamined Patent Publication No. 8-128919 discloses a technique of forming narrow plate springs around a slider supporting part of a load beam by etching or press. This technique deforms the narrow plate springs in a thickness direction, which needs fine processes because the narrow plate springs must be formed in a small area, to deform the shape of the load beam, vary the spring constant thereof, and deteriorate quality.